RU2159146C2 - Method of cleaning gases from selenium hexafluoride - Google Patents

Abstract

FIELD: methods of cleaning gases from selenium hexafluoride. SUBSTANCE: method consists in adsorption of selenium hexafluoride on copper powder at elevated temperature. EFFECT: enhanced efficiency. 2 tbl, 2 ex

Description

 The invention relates to methods for purifying gases from selenium hexafluoride.

 A known method of purification of gases from fluorine and fluorine-containing gases, in particular from tellurium fluorides, molybdenum, uranium and other gases, by adsorption on solid sorbents. As the adsorbents of fluorine and fluorine-containing gases, for example, aluminum oxide, a chemical lime scavenger are used (Galkin NP, Zaitsev VA, Seregin MB. Capture and processing of fluorine-containing gases. - M.: Atomizdat, 1975, p. .145-146).

A known method of purification of gaseous media from trace elements of compounds of selenium (selenium dioxide), arsenic, fluorine and tellurium on an adsorbent that is a carrier (silica gel), modified by an adsorbing substance - titanium, or zirconium, or hafnium, or cerium (aut. St. USSR 762940 , publ. BI N 34.09.15.80, MKI B 01 D 53/02). Silica gel is modified with titanium or other specified substances by sorption of the latter from a solution, followed by calcination at a temperature of 400 ^o C for 4.5 hours. The degree of purification of gaseous media by adsorption on these adsorbents is 97%.

A known method of purification of gases from microimpurities of compounds of selenium (selenium dioxide), fluorine and other impurities by adsorption. A gas mixture containing impurities at a temperature of 350 ^o C is passed through a sorbent bed with a gas residence time of 3.5 s in the sorbent bed until the recoverable components slip through (ed. St. USSR N 889062, publ. 15.12.81, BI N 46, MKI B 01 D 53/02). Thorium dioxide, or cerium oxide, or hafnium dioxide, or titanium dioxide are used as adsorbent. These adsorbents are obtained by calcining the corresponding metal hydroxides at 400 ^o C. the Degree of purification of the gas mixture from impurities is 97.5 - 98%.

The experiments showed the unsuitability of known methods for purification of gases from selenium hexafluoride. The sorption capacity of known sorbents with respect to selenium hexafluoride is less than 0.01 wt.% (Experiments on the adsorption of selenium hexafluoride were carried out at a temperature of 100-300 ^° C and a gas pressure of 10-350 mm Hg). Gas purification from selenium hexafluoride practically does not occur.

 The objective of the invention is to develop a method of purification of gases from selenium hexafluoride.

 The problem is achieved in that in the method of purification of gases from selenium hexafluoride by adsorption at elevated temperature, the adsorption of selenium hexafluoride is carried out on copper powder.

The method uses an adsorbent of selenium hexafluoride, consisting of a copper powder and a carrier selected from a number of chemical scavenger lime, activated alumina, sodium fluoride, in the following ratio, wt.%:
Copper Powder - 8-10
Media - Other
Experiments were conducted to determine the sorption capacity of copper powder with respect to selenium hexafluoride.

In the experiments used copper powder with a specific surface of 7-8 m ² / g, bulk density of 0.4-0.45 g / cm ² and a dispersion of 0.7-0.8 μm, containing copper oxides up to 10 wt.%.

Copper powder with a copper oxide content of 8 wt.% Was treated with selenium hexafluoride at a temperature of 200 ^o C. The experiments were carried out at a gas pressure of 10, 20, 30, 60, 100 and 150 mm Hg. The treatment was carried out until the sorbent was completely saturated, determined by the termination of the interaction of selenium hexafluoride with the adsorbent, after which the adsorbent capacity was determined by selenium hexafluoride by chemical analysis methods. The results of the experiments are presented in table 1.

Copper powder with a copper oxide content of 8 wt.% Was treated with selenium hexafluoride at a gas pressure of 80 mm Hg. The experiments were carried out at a temperature of 100, 200, 300 ^o C. The treatment was carried out until the sorbent was completely saturated, determined by the termination of the interaction of selenium hexafluoride with the adsorbent, after which the adsorbent capacity was determined by chemical analysis of selenium hexafluoride. The results of the experiments are presented in table 2.

 As can be seen from the tables, the sorption capacity of the copper powder with respect to selenium hexafluoride reaches 47 wt.%.

 The purification of gases from selenium hexafluoride is as follows.

For gas purification from selenium hexafluoride, an adsorbent is used that contains a granular or pelletized carrier, a lime chemical scavenger, activated alumina, sodium fluoride, and copper powder in the following ratio of components, wt.%:
Copper Powder - 8-10
Media - Other
In the experiments used copper powder with a specific surface of 7-8 m ² / g, bulk density of 0.4-0.45 g / cm ² and a dispersion of 0.7-0.8 μm, containing copper oxides up to 10 wt.%, Chemical lime absorber according to GOST 6755-88, activated alumina according to GOST 8136-86, sodium fluoride.

 The adsorbent is prepared by mechanical mixing of copper powder and granules or tablets of the carrier. Due to its good adhesive properties, copper powder is retained on the surface of granules or tablets.

A gas mixture containing nitrogen and selenium hexafluoride is passed through an adsorbent bed at a given adsorbent temperature (experiments were carried out at an adsorbent temperature of 100-300 ^° C), a gas mixture pressure of 1 atm and at various partial pressures of selenium hexafluoride.

Example 1. A gas mixture consisting of nitrogen and selenium hexafluoride with a content of the latter 113 mg / l was passed at a rate of 12 l / min through a nickel column with a diameter of 50 mm, in which an adsorbent in an amount of 1 kg containing copper powder (10 wt. %) and a chemical scavenger calcareous (90 wt.%). The gas was purified from selenium hexafluoride at an adsorbent temperature of 300 ^° C. At the outlet of the column, the gas mixture was analyzed for the content of selenium hexafluoride by the IR spectrometric method. After passing 70 l of the gas mixture, a breakthrough of selenium hexafluoride of 5 mg / l was detected. The degree of purification was 95.6%.

Example 2. A gas mixture consisting of nitrogen and selenium hexafluoride with a content of the latter 1130 mg / l was passed at a rate of 2.5 l / min through a nickel column with a diameter of 50 mm, in which an adsorbent in an amount of 1 kg containing copper powder (10 wt. .%) and a chemical scavenger calcareous (90 wt.%). The gas was purified from selenium hexafluoride at an adsorbent temperature of 200 ^° C. At the outlet of the column, the gas mixture was analyzed for the content of selenium hexafluoride by the IR spectrometric method. After passing 35 l of the gas mixture, a breakthrough of selenium hexafluoride of 5 mg / l was detected. The degree of purification was 99.5%.

 Studies have shown that the same degree of gas purification from selenium hexafluoride is achieved when activated or sodium fluoride is used as a carrier of alumina.

 Using the proposed method allows the purification of gases from selenium hexafluoride.

Claims (1)

 The method of purification of gases from selenium hexafluoride, which consists in the adsorption of selenium hexafluoride by copper powder at elevated temperature.

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